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12th Class Physics Electric Charges and Fields Question Bank MCQ - Electric Charges and Fields

  • question_answer
    A particle of mass \[{{10}^{-3}}kg\] and charge \[5\mu C\] is thrown at a speed of \[20\,m{{s}^{-1}}\] against a uniform electric field of strength\[2\times {{10}^{5}}\,N{{C}^{-1}}\]. The distance travelled by particle before coming to rest is:  

    A) 0.1 m                           

    B) 0.2 m   

    C) 0.3 m                           

    D) 0.4 m

    Correct Answer: B

    Solution :

    (b) 0.2m \[F=qE=5\times {{10}^{-6}}\times 2\times {{10}^{5}}=1N\] Since, the particle is thrown against the field \[\therefore \,\,a=-F/m=-\frac{1}{{{10}^{-3}}}=-{{10}^{3}}\,m{{s}^{-2}}\] As \[{{v}^{2}}-{{u}^{2}}=2as\] \[\therefore \,\,{{0}^{2}}-{{\left( 20 \right)}^{2}}=2\times \left( -{{10}^{3}} \right)\times s\] Or \[s=0.2\,m\]


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